MIT engineers develop CrSBr-based transistor
MIT researchers with colleagues from the University of Chemistry and Technology in Prague have used 2D CrSBr, a van der Waals antiferromagnetic semiconductor, to create a transistor that could enable smaller, faster, and more energy-efficient circuits.
Their paper 'Large Magnetoresistance in an Electrically Tunable van der Waals Antiferromagnet' has just been published in Physical Review Letters.
“People have known about magnets for thousands of years, but there are very limited ways to incorporate magnetism into electronics. We have shown a new way to efficiently utilise magnetism that opens up a lot of possibilities for future applications and research,” says Chung-Tao Chou, an MIT graduate student in the departments of Electrical Engineering and Computer Science (EECS) and Physics, and co-lead author of a paper.
The interplay between magnetic order and electronic band structure in antiferromagnets has garnered increasing interest due to its potential for spintronic applications. In this work, the researchers have successfully combined magnetism and semiconductor physics to realise useful spintronic devices.
The researchers have replaced the silicon in the surface layer of a transistor with 2D CrSBr. Due to the material’s structure, researchers found they can switch between two magnetic states very cleanly. “One of the biggest challenges we faced was finding the right material. We tried many other materials that didn’t work,” Chou says.
To make a transistor, the researchers pattern electrodes onto a silicon substrate, then carefully align and transfer the 2D material on top. They use tape to pick up a tiny piece of material, only a few tens of nanometers thick, and place it onto the substrate.
“A lot of researchers will use solvents or glue to do the transfer, but transistors require a very clean surface. We eliminate all those risks by simplifying this step,” Chou says.
This lack of contamination, they say, enables their device to outperform existing magnetic transistors. Most others can only create a weak magnetic effect, changing the flow of current by a few percent or less. Their new transistor can switch or amplify the electric current by a factor of ten.
They use an external magnetic field to change the magnetic state of the material, switching the transistor using significantly less energy than would usually be required. The material also allows them to control the magnetic states with electric current. The researchers add that the material’s magnetic properties could also enable transistors with built-in memory, simplifying the design of logic or memory circuits.
“Now, not only are transistors turning on and off, they are also remembering information. And because we can switch the transistor with greater magnitude, the signal is much stronger so we can read out the information faster, and in a much more reliable way,” says Luqiao Liu, an associate professor at EECS MIT.
Building on this demonstration, the researchers plan to further study the use of electrical current to control the device. They are also working to make their method scalable so they can fabricate arrays of transistors.
This research was supported, in part, by the Semiconductor Research Corporation, the US Defense Advanced Research Projects Agency (DARPA), the US National Science Foundation (NSF), the US Department of Energy, the US Army Research Office, and the Czech Ministry of Education, Youth, and Sports.
